SDS-PAG electrophoresis showed that the polyhedron proteins of Leucaia separata nuclear polyhedrosis virus(LsNPV)was consisted of several polypeptides, the major band of MW 32kD was the major structural polypeptides of polyhedra. Amino acid composition of 32kD protein was analyzed after purification by chramatography of Sephacryl S-200 column. The cell growth of three tumor (Hela, HLAMP, HICAM)was inhibited by 32kD protein, DNA replication labeling with ~3H-TdR recognized the result.